IsExternalInit.cs

using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;

// <auto-generated>
//   This code file has automatically been added by the "IsExternalInit" NuGet package (https://www.nuget.org/packages/IsExternalInit).
//   Please see https://github.com/manuelroemer/IsExternalInit for more information.
//
//   IMPORTANT:
//   DO NOT DELETE THIS FILE if you are using a "packages.config" file to manage your NuGet references.
//   Consider migrating to PackageReferences instead:
//   https://docs.microsoft.com/en-us/nuget/consume-packages/migrate-packages-config-to-package-reference
//   Migrating brings the following benefits:
//   * The "IsExternalInit" folder and the "IsExternalInit.cs" file don't appear in your project.
//   * The added file is immutable and can therefore not be modified by coincidence.
//   * Updating/Uninstalling the package will work flawlessly.
// </auto-generated>

#region License

// MIT License
// 
// Copyright (c) Manuel Römer
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#endregion

#if !ISEXTERNALINIT_DISABLE
#nullable enable
#pragma warning disable

namespace System.Runtime.CompilerServices
{
    /// <summary>
    ///     Reserved to be used by the compiler for tracking metadata.
    ///     This class should not be used by developers in source code.
    /// </summary>
    /// <remarks>
    ///     This definition is provided by the <i>IsExternalInit</i> NuGet package
    ///     (https://www.nuget.org/packages/IsExternalInit).
    ///     Please see https://github.com/manuelroemer/IsExternalInit for more information.
    /// </remarks>
#if !ISEXTERNALINIT_INCLUDE_IN_CODE_COVERAGE
    [ExcludeFromCodeCoverage]
    [DebuggerNonUserCode]
#endif
    internal static class IsExternalInit
    {
    }
}

#pragma warning restore
#nullable restore
#endif // ISEXTERNALINIT_DISABLE
// https://github.com/dotnet/runtime/blob/419e949d258ecee4c40a460fb09c66d974229623/src/libraries/System.Private.CoreLib/src/System/Index.cs
// https://github.com/dotnet/runtime/blob/419e949d258ecee4c40a460fb09c66d974229623/src/libraries/System.Private.CoreLib/src/System/Range.cs


namespace System
{
    /// <summary>Represent a type can be used to index a collection either from the start or the end.</summary>
    /// <remarks>
    ///     Index is used by the C# compiler to support the new index syntax
    ///     <code>
    /// int[] someArray = new int[5] { 1, 2, 3, 4, 5 } ;
    /// int lastElement = someArray[^1]; // lastElement = 5
    /// </code>
    /// </remarks>
    internal readonly struct Index : IEquatable<Index>
    {
        private readonly int _value;

        /// <summary>Construct an Index using a value and indicating if the index is from the start or from the end.</summary>
        /// <param name="value">The index value. it has to be zero or positive number.</param>
        /// <param name="fromEnd">Indicating if the index is from the start or from the end.</param>
        /// <remarks>
        ///     If the Index constructed from the end, index value 1 means pointing at the last element and index value 0 means
        ///     pointing at beyond last element.
        /// </remarks>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public Index(int value, bool fromEnd = false)
        {
            if (value < 0) throw new ArgumentOutOfRangeException(nameof(value), "value must be non-negative");

            if (fromEnd)
                _value = ~value;
            else
                _value = value;
        }

        // The following private constructors mainly created for perf reason to avoid the checks
        private Index(int value)
        {
            _value = value;
        }

        /// <summary>Create an Index pointing at first element.</summary>
        public static Index Start => new(0);

        /// <summary>Create an Index pointing at beyond last element.</summary>
        public static Index End => new(~0);

        /// <summary>Create an Index from the start at the position indicated by the value.</summary>
        /// <param name="value">The index value from the start.</param>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Index FromStart(int value)
        {
            if (value < 0) throw new ArgumentOutOfRangeException(nameof(value), "value must be non-negative");

            return new Index(value);
        }

        /// <summary>Create an Index from the end at the position indicated by the value.</summary>
        /// <param name="value">The index value from the end.</param>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Index FromEnd(int value)
        {
            if (value < 0) throw new ArgumentOutOfRangeException(nameof(value), "value must be non-negative");

            return new Index(~value);
        }

        /// <summary>Returns the index value.</summary>
        public int Value
        {
            get
            {
                if (_value < 0)
                    return ~_value;
                return _value;
            }
        }

        /// <summary>Indicates whether the index is from the start or the end.</summary>
        public bool IsFromEnd => _value < 0;

        /// <summary>Calculate the offset from the start using the giving collection length.</summary>
        /// <param name="length">The length of the collection that the Index will be used with. length has to be a positive value</param>
        /// <remarks>
        ///     For performance reason, we don't validate the input length parameter and the returned offset value against negative
        ///     values.
        ///     we don't validate either the returned offset is greater than the input length.
        ///     It is expected Index will be used with collections which always have non negative length/count. If the returned
        ///     offset is negative and
        ///     then used to index a collection will get out of range exception which will be same affect as the validation.
        /// </remarks>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int GetOffset(int length)
        {
            var offset = _value;
            if (IsFromEnd)
                // offset = length - (~value)
                // offset = length + (~(~value) + 1)
                // offset = length + value + 1

                offset += length + 1;
            return offset;
        }

        /// <summary>Indicates whether the current Index object is equal to another object of the same type.</summary>
        /// <param name="value">An object to compare with this object</param>
        public override bool Equals(object? value)
        {
            return value is Index && _value == ((Index)value)._value;
        }

        /// <summary>Indicates whether the current Index object is equal to another Index object.</summary>
        /// <param name="other">An object to compare with this object</param>
        public bool Equals(Index other)
        {
            return _value == other._value;
        }

        /// <summary>Returns the hash code for this instance.</summary>
        public override int GetHashCode()
        {
            return _value;
        }

        /// <summary>Converts integer number to an Index.</summary>
        public static implicit operator Index(int value)
        {
            return FromStart(value);
        }

        /// <summary>Converts the value of the current Index object to its equivalent string representation.</summary>
        public override string ToString()
        {
            if (IsFromEnd)
                return "^" + (uint)Value;

            return ((uint)Value).ToString();
        }
    }

    /// <summary>Represent a range has start and end indexes.</summary>
    /// <remarks>
    ///     Range is used by the C# compiler to support the range syntax.
    ///     <code>
    /// int[] someArray = new int[5] { 1, 2, 3, 4, 5 };
    /// int[] subArray1 = someArray[0..2]; // { 1, 2 }
    /// int[] subArray2 = someArray[1..^0]; // { 2, 3, 4, 5 }
    /// </code>
    /// </remarks>
    internal readonly struct Range : IEquatable<Range>
    {
        /// <summary>Represent the inclusive start index of the Range.</summary>
        public Index Start { get; }

        /// <summary>Represent the exclusive end index of the Range.</summary>
        public Index End { get; }

        /// <summary>Construct a Range object using the start and end indexes.</summary>
        /// <param name="start">Represent the inclusive start index of the range.</param>
        /// <param name="end">Represent the exclusive end index of the range.</param>
        public Range(Index start, Index end)
        {
            Start = start;
            End = end;
        }

        /// <summary>Indicates whether the current Range object is equal to another object of the same type.</summary>
        /// <param name="value">An object to compare with this object</param>
        public override bool Equals(object? value)
        {
            return value is Range r &&
                   r.Start.Equals(Start) &&
                   r.End.Equals(End);
        }

        /// <summary>Indicates whether the current Range object is equal to another Range object.</summary>
        /// <param name="other">An object to compare with this object</param>
        public bool Equals(Range other)
        {
            return other.Start.Equals(Start) && other.End.Equals(End);
        }

        /// <summary>Returns the hash code for this instance.</summary>
        public override int GetHashCode()
        {
            return Start.GetHashCode() * 31 + End.GetHashCode();
        }

        /// <summary>Converts the value of the current Range object to its equivalent string representation.</summary>
        public override string ToString()
        {
            return Start + ".." + End;
        }

        /// <summary>Create a Range object starting from start index to the end of the collection.</summary>
        public static Range StartAt(Index start)
        {
            return new Range(start, Index.End);
        }

        /// <summary>Create a Range object starting from first element in the collection to the end Index.</summary>
        public static Range EndAt(Index end)
        {
            return new Range(Index.Start, end);
        }

        /// <summary>Create a Range object starting from first element to the end.</summary>
        public static Range All => new(Index.Start, Index.End);

        /// <summary>Calculate the start offset and length of range object using a collection length.</summary>
        /// <param name="length">The length of the collection that the range will be used with. length has to be a positive value.</param>
        /// <remarks>
        ///     For performance reason, we don't validate the input length parameter against negative values.
        ///     It is expected Range will be used with collections which always have non negative length/count.
        ///     We validate the range is inside the length scope though.
        /// </remarks>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (int Offset, int Length) GetOffsetAndLength(int length)
        {
            int start;
            var startIndex = Start;
            if (startIndex.IsFromEnd)
                start = length - startIndex.Value;
            else
                start = startIndex.Value;

            int end;
            var endIndex = End;
            if (endIndex.IsFromEnd)
                end = length - endIndex.Value;
            else
                end = endIndex.Value;

            if ((uint)end > (uint)length || (uint)start > (uint)end)
                throw new ArgumentOutOfRangeException(nameof(length));

            return (start, end - start);
        }
    }
}

namespace System.Runtime.CompilerServices
{
    internal static class RuntimeHelpers
    {
        /// <summary>
        ///     Slices the specified array using the specified range.
        /// </summary>
        public static T[] GetSubArray<T>(T[] array, Range range)
        {
            if (array == null) throw new ArgumentNullException(nameof(array));

            (var offset, var length) = range.GetOffsetAndLength(array.Length);

            if (default(T) != null || typeof(T[]) == array.GetType())
            {
                // We know the type of the array to be exactly T[].

                if (length == 0) return Array.Empty<T>();

                var dest = new T[length];
                Array.Copy(array, offset, dest, 0, length);
                return dest;
            }
            else
            {
                // The array is actually a U[] where U:T.
                var dest = (T[])Array.CreateInstance(array.GetType().GetElementType(), length);
                Array.Copy(array, offset, dest, 0, length);
                return dest;
            }
        }
    }
}